That is not possible with bitcoins.
Under the circumstances, en interrogation in England is the best solution for every parties. If, following the interrogation, formal charges are layed and is is accused of rape, his situation will change anyway and probably won't have the choice to face the charges there, regardless where he is.
I think for some parties it is best when he stays locked into that embassy. So they are not gonna change anything and Assange must stay there until he is willing to risk to go to Sweden.
And I can't believe that the NASA will not use it in the future, the article also gives no real reason for that.